How to "revert" object along some axis?
You can use the mirror transform to 'revert' your object.
And if you don't like negative scale, just apply the scale.  

Mirror object: Object > Mirror
Apply Scale: Object > Apply > Scale  

How to mirror an object and apply scale.


Note:
Applying negative scale can flip your normals orientation.
Check your normals after that, so they're not inverted.